TECHNICAL PUBLICATIONS:

Printed polymer transistor arrays for displays and imaging

Golden Gate Polymer Forum

Organic semiconductors are an attractive transistor technology for inexpensive displays and image sensors. Polymers offer low temperature solution processing on flexible substrates at low cost. Direct writing of active materials minimizes both the number of processing steps and the use of materials, and therefore also the cost of device fabrication. Direct writing of mask material for feature definition is also a simple and inexpensive patterning process. We have developed a process to fabricate arrays of organic transistors (OTFTs) using these techniques to completely replace photolithography. In this multiple-mask process, metal for the source/drain contacts and the gate are patterned using jet-printed wax as a resist for wet etching, and the organic semiconducting polymer is deposited using inkjet printing and other fluidic deposition processes. Prototype active matrix TFT arrays are fabricated on a 300-micron pitch using a process with minimum feature size of 40 microns and alignment between layers of better than 10 microns. The talk will describe the processing approaches and compare alternative techniques to pattern the semiconductor. Characterization of our printed organic transistors shows field effect mobility and on/off ratios that compare favorably with OTFTs fabricated by spin-casting.